In valves of the cone valve type, use is made of a valve cone for controlling a flow in coaction with a seat. Such valve cones can be designed in various ways.
DE-10 62 507 discloses a valve cone, which in a first end is connected to a valve stem and in a second end is arranged to cooperate with a valve seat. When the valve is closed, the cone is pressed by the valve stem against the seat for sealing against the same (pressing closure).
The cone is formed with a radially through slot extending in the axial direction in the form of a V. The cone is opened and closed in the axial direction and is controlled in the radial direction by means of the valve stem.
With this valve design, good controllability can be achieved merely within a very limited range. Besides, a tapering cone causes great changes in flow close to the closed position, thereby preventing good controllability for small flows.
Since the axial guiding of the cone is effected on the one hand by means of the stem and, on the other hand, at an axial distance from the seat, the cone produces and conveys vibrations when a fluid flows through the valve, which in itself results in a high sound level and the valve being worn.
DE 18 16 002 discloses an asymmetrical fish-mouth-like valve cone with a recessed groove, which via an end portion of the cone extends axially from one side to the opposite side. The groove extends over different distances on the different sides and the respective end portions of the groove are narrow in the circumferential direction and deep in the radial direction.
The last-mentioned cone is, owing to its asymmetry, sensitive to being set at an angle and, in operation, is subjected to uneven loads, which causes premature wear of the valve.
The valve cones described above both suffer from the drawback of having a complicated shape, which implies that they are complicated and expensive to manufacture. The complicated shape also results in the cones being difficult to calculate and dimension.
Moreover, the two valve cones described above are intended to be operated with pressing closure, in which the valve stem is subjected to bending stress when the valve is closed. The harder the valve is pressed against the seat, the greater bending stress is produced. This leads to the stem gradually being bent, in which case the cone can be located off-centre in the seat and cause uneven wear thereof.
EP-0 457 132 discloses a valve cone having V-shaped axial grooves of triangular cross-section and different length. The valve cone is intended for the control of flows of liquid food products and for operating with so-called pressing closure.
This cone has good controllability merely within a very limited range. Large flows through the triangular grooves are not allowed.
Information sheets from Hansen Technologies Corporation, Burr Ridge, Ill., USA, describe a valve having a V gate and four V-shaped recesses which define a crown. At the lower part of the crown, the recesses immediately have a relatively large radial depth. The valve stem is connected to the open end of the crown, and contrary to those described above, the cone is intended for pulling closure. By pulling closure is meant in connection with the invention that the valve cone, when the valve is closed, is actuated by means of an actuator, for instance a valve stem, with a pulling force acting in the direction of the closed position, contrary to pressing closure.
This construction has a complicated form and thus is difficult to calculate and expensive to manufacture. This design can only with great difficulty be obtained by machining. Moulding such a valve cone causes several drawbacks. The production will be expensive since expensive tools are necessary. Besides, the tolerance spread will be broad in such a method.